In most computer systems there are a series of interconnected logical modules which are (often housed on logic cards) and these modules are interconnected together for data, command, and status information transfers. The actual physical interconnection between these modules may consist of cables, printed-circuit boards, backplane wiring, or plug-in mother boards. Quite commonly, a backplane will provide connective slots for insertion of logical modules residing on PC boards.
In such multiple module systems which are interconnected to each other, some of the modules will always be present, for example, the processor module will always be present. Likewise generally a main memory module will also always be present. In this disclosure, such "always present" modules will be referred to as "standard modules".
However, some of the modules in the interconnected system may also be what are called pluggable system "options" or optional modules. In certain cases these may not be present and in certain cases these may be present in a specific system. In the discussions herein, these options will be referred to as "optional modules". Art example of an optional module would be such type which might be called a "Cache Memory Module". Such types of an optional module can be added to an interconnected system in order to increase system performance.
Normally, it is essential for the so called standard modules to be informed of or "aware of" the presence or absence of the optional modules to which they may or may not communicate. In many systems, this detection is actually accomplished by the activities of human personnel at the time of the system manufacture or the time of system installation. In these type systems, the standard modules must be physically changed or reconfigured manually in some manner to indicate the status of the optional module.
However, it is most desirable and it is far more economically efficient, if all of the standard modules of the same type (for example processor cards) are manufactured and then inventoried identically so that in this fashion there is no special handling required during manufacture or installation.
The problem arises in that standard modules will generally act one way when there is no optional module present and the standard module will operate in another way when an optional module is present. Thus the problem often occurs of how to keep standard modules informed of the presence of, or of the absence of, the optional module situation.
This disclosure describes a method by which the actual standard hardware modules can be enabled to detect the presence of any optional modules. With the method and system disclosed herein, the standard modules will no longer need any special reconfiguration work which is based upon the state of the optional modules in the system. Also, the presently described method in this system presents a method by which the standard modules, upon detecting the state of the optional modules, will modify their own logic accordingly. In this fashion, all of the standard modules of the same type are maintained in an identical fashion and will need no special human reconfiguration, rewiring or redesign.